As noted by [1]} and [2]}, different systematics on the spectra such as micro-tellurics, tellurics, colour variation due to airmass and detector stitching can also affect the RV, on timescales very different from those modelled with a single GP kernel. YARARA [2]} and WOBBLE [4]} were developed on this ground as post-processing pipelines to cope with these features in the spectra. YARARA uses Principal Component Analysis on HARPS spectral time series to correct for the known non-planetary systematics without using models for the different effects. WOBBLE is a data-driven method that can be used to infer the stellar spectra, telluric spectra and RVs simultaneously from the data [4]}.
